It is true. Have an example load of pictures: https://duckduckgo.com/?q=street+light+electric+car+charging.... My city (not London!) has had them for >3 years that I remember.

The main difference is that (a) each street light is actually ~ 10W, and (b) the wiring is massively over-specified. Quoting from a local authority source for street lights, [1], the minimum conductor area allowed (for the 220-270 VAC supply) is 6 mm^2, for a total thermal current limit of around ~55A. If you have, say, 100 lamps on a single "ring main", you still only have a power draw of ~1 kW, where the cable is rated to 55 V x 220 A ≈12.1 kW minimum.

[1] https://www.durham.gov.uk/media/3075/Street-Lighting-Specifi...

Tesla's new fast chargers support 250kw peak per car. So even 12kw is nothing to write home about. How many poles is that shared between? If it's more than 4 then it's not really enough. I suspect the reason the conductor is over specified though is to avoid voltage dropping outside of the 10% range it's allowed.

What's the carbon footprint of all the extra copper needed for the heavy gauge wiring?

I was under the impression that you're not guaranteed 3Kw from everywhere, probaby just a trickle charge overnight...

3kw is a trickle charge. Even the previous generation leaf had a 24kwh battery. From flat to fully charged would be overnight. 60kwh is more like what you need for similar range to a petrol car.